No one seems to be talking about this being a normal part of the stage of life you're in. The 40's are typically the most miserable decade in a person's life, and this is well documented. The major caveat to that is "I know I'm depressed and have been for the majority of my life" - which adds a different wrinkle. But that it's getting worse now is to be expected.
Some readings, which have been helpful for me (I'm also in my 40's):